Especially in the food, cosmetics and drug industry, but also in other fields, there is a need to be able to perform in a rational manner durability treatment or sterilisation of a pumpable material, such as a liquid or suspension, in larger batches than the end-user or consumer containers which are intended to hold the material, without risking contamination of the material with pollutants, such as microorganisms, during, and particularly after, the actual process of filling the end-user or consumer containers. In connection with activities with stringent cleanliness requirements, all objects and surfaces that have contacted non-cleaned air are considered contaminated. Via these objects and surfaces, pollutants may enter the pumpable material in connection with treatment and emptying and have a detrimental effect on its durability, taste, smell and the like.
Such durability treatment in large batches occurs by pasteurisation, i.e. heating of the material, in large tanks or the like. However, such a method involves drawbacks owing to the fact that much energy must be supplied in pasteurisation in order to heat the entire volume, and the process is time-consuming on the one hand because of the time it takes to heat the entire volume and, on the other hand, because the heat treatment must proceed for a certain length of time for all microorganisms safely to be rendered harmless. For instance, the outer parts of the liquid volume may be subjected to extremely long heat treatment for the central parts to obtain an acceptable heat treatment time. Many pumpable materials, especially foodstuffs, are sensitive to high temperatures and long heat treatments and may be negatively affected, with regard to consistency as well as smell and taste, during such treatments.
Durability treatment of pumpable materials is also known to take place by radioactive irradiation. In the case of irradiation of large batches, the problem arises that radiation efficiency decreases with the length of the distance that the radiation must cover in the pumpable material. There is thus a risk that the radiation dose in the centre of the liquid volume will be too small to achieve a sufficient durability treating effect. Alternatively, such high radiation doses must be applied that other negative consequences arise, such as problems of the working environment.
The most common method in heat treatment and irradiation is to carry out the treatment in a continuous flow in a portion of a pipe. In the heat treatment, the pumpable material is caused to flow past heat exchangers and be heated by them whereas in irradiation the pumpable material flows through an irradiated area in the pipe. In such a method, the drawbacks in connection with treatment of large batches at a time are eliminated, viz. that the outer portions of the volume will be excessively treated while the central portions tend to be insufficiently treated. However, there remains the problem that heat treatment requires much energy and certain materials can be negatively affected while irradiation may involve problems of the working environment. However, also the problem remains that the pumpable material must be treated in a sterile manner in the continued handling, such as filling end-user containers, which must normally be carried out in immediate connection with the durability treatment owing to the difficulties in intermediate storing and transporting the pumpable material before filling the end-user containers.
DE 3 510 859 discloses durability treatment or sterilisation of a pumpable material, which however is not described in more detail, and subsequently filling the material into bulk containers, so-called bag-in-box bulk containers consisting of a plastic bag enclosed in a cardboard box or the like. When the bulk container is to be filled or emptied, this must take place in a sterile manner. For this reason, a tapping device is connected to a sealed tapping flange on the bulk container in such a manner that the tapping device, in a first step, is arranged round the tapping flange, and then the space between the tapping flange and the tapping device is sterilised by steam. Finally, a cap nut of the tapping device is screwed onto an outer thread of the tapping flange so that a pointed hose connecting piece of the tapping device penetrates a pharmaceutical injection plug or a sealing washer in the tapping flange. Before filling the pumpable material into the bulk container, the container must be carefully cleaned by means of a cleaning agent or sterilised by, for instance, irradiation. Such a method enables intermediate storing and/or transporting of the pumpable material before filling it into end-user containers. The method involves, however, a complicated and time-consuming procedure of sterile filling of the durability treated pumpable material into the bulk container as well as sterile emptying of the same. Moreover the bulk container must be sterilised separately before filling, for instance by irradiation, which results in an additional time-consuming step of handling.
Durability treatment in the form of high pressure treatment in large batches has also been tested. Then the pumpable material is filled directly into the high pressure press so as to be in contact with the boundary walls of the press chamber. This requires, however, cleaning of the press between different shifts and also between high pressure treatments of different types of pumpable materials. The difficulty in cleaning the press therefore often results in potential colonies of bacteria of the pumpable material remaining in corners, bends and the like. In this case there is also a risk that a pressure medium, such as water or oil, leaks into the press chamber and is mixed with the pumpable material.
The normal process in durability treatment by high pressure has therefore been to subject the pumpable material to high pressure treatment in the end-user containers. In the high pressure treatment, the material is subjected to a pressure of at least 2000 bar and preferably 6000–7000 bar, at which pressure certain microorganisms and enzymes are killed or inactivated. This is possible only on the condition that the container is suited for such high pressure treatment, which requires, inter alia, the container to be flexible in at least one direction since the volume of a liquid or suspension is compressed by about 15% in high pressure treatment to this pressure. Moreover, there should be no gas in the container since this would cause compression to increase drastically. The drawback of such a process is that end-user containers are usually relatively small and high pressure treatment thereof one by one will not be rational. Certainly it is in many cases possible to stack a large number of end-user containers in a high pressure press and subject them to high pressure treatment in one and the same step, but depending on the shape of the end-user containers, the volume of the high pressure press will usually be poorly utilised, and besides a further, time-consuming operation will be added, viz. stacking the end-user containers in the manner that is most optimal for pressing. The process also limits the type of end-user containers that may be used since not all are suited for high pressure treatment, such as glass bottles and other hard containers.
In addition to the above drawbacks, there are a number of advantages of high pressure treatment compared with other methods of durability treatment. For instance, the high pressure treatment results in a durability treatment which is kind to the pumpable material, in comparison with heat treatment, so-called pasteurisation, which must be carried out at such a high temperature and for such a long time that the qualities of the product, such as smell, taste and consistency, risk being deteriorated. In heat treatment of large batches of a pumpable material, the outer portions of the volume may also be damaged owing to excessive action of heat for too long a period while the central portions will be insufficiently treated owing to insufficient action of heat for too short a period and therefore risk obtaining too short a shelf life. The drawback of high pressure treatment is that up till now it could not be performed in a simple, rational and hygienic manner.